Gas turbine engines (GTE) convert potential energy associated with air and fuel into energy, primarily in the form of mechanical rotation and heat. A conventional GTE may include a compressor assembly, a combustor assembly, and a turbine assembly. During operation, air is drawn into and compressed within the compressor assembly. The combustor assembly receives compressed air from the compressor assembly, supplies fuel thereto, and ignites and combusts the compressed air and fuel mixture. The combustion products are supplied to the turbine assembly and expanded to cause a turbine rotor to rotate, thereby producing rotational energy. The turbine may be coupled to the compressor assembly and one or more systems that use the rotational energy and/or thermal energy developed by the turbine. The exhaust generated is typically discharged into an exhaust outlet.
Under certain conditions, it is known to bleed a portion of the compressed air from the compressor assembly before it is permitted to mix with fuel and ignite during combustion. The compressed air bypassing the combustion process is known as bleed air, and the compressed air that is used in the combustion process is known as combustion air. There are various reasons for bleeding air before combustion including, for example, stabilizing combustion and controlling engine performance. The bleed air may be discharged directly to the atmosphere or into an exhaust outlet device to combine the bleed air and turbine exhaust before expelling both to the atmosphere. The bleed air discharged into the exhaust outlet device may have relatively high velocity (e.g., sonic) and pressure and may create shock waves that generate vibrations within the exhaust outlet device. The vibrations may cause undesirable noise and may fatigue the exhaust outlet device or other downstream components over time.
A GTE including a bleed air assembly is disclosed in U.S. Pat. No. 6,543,234 B2 issued to Anand et al. ('234 patent). The '234 patent discloses a gas turbine system including a compressor, a combustor, and a turbine powering a load. The '234 patent discloses a bleed air circuit that removes bleed air from the compressor and discharges it into an exhaust stack. The bleed air circuit includes a bypass valve to control the percentage of compressed air that bypasses the combustor as bleed air. The '234 patent also discloses that a portion of the bleed air may be expanded via an air expander to reduce pressure upstream of the exhaust stack.
The system of the '234 patent may insufficiently reduce vibrations in the exhaust stack because only a portion of the bleed air is designed to pass through the air expander. The system of the '234 patent may also be expensive and complex because the bleed air circuit includes a plurality of valves and other components to direct the bleed air from an air bleed inlet to the exhaust stack.